Add reverseUsingStringBuilder method to reverse a string (#6182)

src/main/java/com/thealgorithms/strings/ReverseString.java

@@ -36,4 +36,25 @@ public final class ReverseString {
         }
         return new String(value);
     }
+
+    /**
+     * Reverse version 3 the given string using a StringBuilder.
+     * This method converts the string to a character array,
+     * iterates through it in reverse order, and appends each character
+     * to a StringBuilder.
+     *
+     * @param string The input string to be reversed.
+     * @return The reversed string.
+     */
+    public static String reverse3(String string) {
+        if (string.isEmpty()) {
+            return string;
+        }
+        char[] chars = string.toCharArray();
+        StringBuilder sb = new StringBuilder();
+        for (int i = string.length() - 1; i >= 0; i--) {
+            sb.append(chars[i]);
+        }
+        return sb.toString();
+    }
 }

src/test/java/com/thealgorithms/strings/ReverseStringTest.java

@@ -25,4 +25,10 @@ public class ReverseStringTest {
     public void testReverseString2(String input, String expectedOutput) {
         assertEquals(expectedOutput, ReverseString.reverse2(input));
     }
+
+    @ParameterizedTest
+    @MethodSource("testCases")
+    public void testReverseString3(String input, String expectedOutput) {
+        assertEquals(expectedOutput, ReverseString.reverse3(input));
+    }
 }